Substrate-type probes formed by a microfabrication technique have recently attracted attentions for electrophysiologically measuring an ion channel in a cell membrane. These probes do not require a skilled operation to insert a micropipette to each cell unlike conventional patch clamp methods, thus being suitable for an automated system having a high throughput.
FIG. 10 is a cross-sectional view of conventional cellular electrophysiology sensor 101 disclosed in Patent Document 1. Cellular electrophysiology sensor 101, a substrate-type probe, includes substrate 102 and electrode bath 103 located above substrate 102. Substrate 102 has through-hole 105 penetrating from an upper surface of substrate 102 to a lower surface of substrate 102.
First electrode 106 is provided in electrode bath 103. Second electrode 107 is provided in through-hole 105. Second electrode 107 is connected to a signal detector via wiring 108.
An operation of cellular electrophysiology sensor 101 will be described below.
First, electrolyte solution 109 and test cell 110 are injected into electrode bath 103. Test cell 110 is captured and held at opening 104 of through-hole 105.
Test cell 110 is sucked with a suction pump from a lower side of through-hole 105 and is retained while attached securely to opening 104. Specifically, through-hole 105 functions as a tip end hole of a micropipette. Thus, while test cell 110 is attached securely to opening 104, a change in a voltage between first electrode 106 and second electrode 107 before and after a reaction is measured, or a change in a current before and after the reaction is measured. Then, a potential difference between outside and inside of the cell is calculated to analyze a function of an ion channel of test cell 110 and a physiological property, such as a pharmacological reaction, of the cell having an electrophysiology property cell.
In conventional cellular electrophysiology sensor 101, test cell 110 captured by through-hole 105 may not be securely attached onto opening 104. When test cell 110 is not attached securely onto opening 104, the cell does not provide a high electrical resistance (a gigaseal) between first electrode 106 and second electrode 107 reproducibly and stably.
Individual test cells 110 have different properties, such as surface property and elasticity. These individual differences influence the gigaseal. Through-hole 105 is very small, and hence, a dust attached to through-hole 105 deteriorates the gigaseal around through-hole 105. This prevents through-hole 105 from sucking and capturing test cell 110 securely and stably, thus deteriorating the gigaseal.    Patent Document 1: WO02/055653